Last spring, a colleague of Walter Noll came to visit. The colleague asked Mr. Noll’s daughter, Virginia Cassidy, what it was like growing up with the mathematician as her dad.

“It was like he was Brad Pitt or something,” Ms. Cassidy said.

Mr. Noll, who died Tuesday at 92, was a professor emeritus of mathematics at Carnegie Mellon University.

It was not always clear, however, that he would be able to enter the field. Noll was born in Berlin, Germany, to Franz and Martha Noll. In high school, he excelled in math and physics.

But World War II interrupted his studies. His family, he wrote, was staunchly anti-Nazi, but they kept their views quiet for fear of retaliation. Mr. Noll was drafted into the German army in 1943, but his son Peter said, he didn’t want to die for his country.

“My principal concern from 1943 until the end of the war was survival,” Mr. Noll wrote, in a diary that he and Peter later translated. “Many of my classmates were killed.”

Soon after his enlistment, Mr. Noll sustained a non-combat injury, spent months in the hospital, and due to an administrative error, spent several more months at home before being re-drafted.

After the war, Noll studied mathematics at the Technical University of Berlin. But he always was freezing and food was scarce. For that reason, Peter said Mr. Noll supported organizations like CARE, which delivered millions of packages to Berlin during the 1948 Soviet blockade.

“He knew what it was like to be hungry and in need and he was helped out,” Peter said.

Times got better: Mr. Noll studied at the Sorbonne in Paris and in 1953 he began a graduate program at Indiana University. He earned his PhD in applied mathematics a year later, then returned to Germany to marry his wife Helga, whom he had met three years earlier.

Mr. Noll got his first U.S. job at the University of Southern California in 1955 before joining the Carnegie Institute of Technology, now Carnegie Mellon, in 1956. He was a fellow of the American Mathematical Society and a founding member of the Society for Natural Philosophy

Mr. Noll was something of a rock star in the areas of thermodynamics and continuum mechanics. He helped to develop the Coleman-Noll procedure, an interpretation of the Second Law of Thermodynamics that “places restrictions on the kind of materials that can occur in nature,” said William J. Hrusa, professor of mathematics at Carnegie Mellon. 

Brian Seguin, an assistant professor at Loyola University of Chicago who was Mr. Noll’s doctoral student from 2010 to 2015, said Mr. Noll also was particularly proud of “Finite-Dimensional Spaces,” a book that reconsiders fundamental concepts in mathematics and, Mr. Seguin said, tries to unify concepts that often are taught separately.  

“He brought a level of clear mathematical thinking to the subject,” Seguin said. 

The importance of education was something he impressed upon his children, sometimes making them write compositions before they could go out, Ms. Cassidy said. He also emphasized the difference between arithmetic and mathematics, where “rote memorization is deadly, while conceptual understanding and problem-solving ability are essential,” he wrote in a 2002 letter to the Pittsburgh Post-Gazette.

Mr. Noll’s wife Helga died in 1976. In 1979, he remarried Mary Strauss-Noll, a Penn State University English professor. He and “Resie”, as Mary was known, took full advantage of Pittsburgh’s culture scene, attending the opera and symphony, and they often visited Mrs. Strauss-Noll’s large family. 

Mr. Noll retired from Carnegie Mellon in 1993, but he still taught, wrote and lectured around the world, particularly in Italy, for most of the rest of his life. His maintained an interest in history, and he enjoyed long conversations and debates. 

Mrs. Strauss-Noll died in 1999. Soon after, Mr. Noll met Marilyn Smith Noll online, and they married in 2000.

“That period we traveled a lot,” Mrs. Noll said. “We went to Turkey and Greece and a lot of different places together. When he was 85, we went snorkeling in the Great Barrier Reef. He said, ‘We better do it now.’ ”

Toward the end of his life, when his health began to fail, Mr. Noll told his wife he was never bored. He was always thinking about mathematics.

At the same time, she said, he was kind.

“He was such a generous, loving man,” she said. “He made my life so happy.”

Mr. Noll is survived by his wife and children, as well as stepchildren Elizabeth Foster of Denver and David and Jonathan Hall of Knoxville, Md.; three grandchildren, seven stepgrandchildren and nine stepgreat-grandchildren.

A memorial service for Mr. Noll will take place at noon on June 21 at the Hunt Botanical Library at Carnegie Mellon.

Contact Emily McConville at emcconville@post-gazette.com or (412) 263-1937. 

First Published: June 11, 2017, 4:00 a.m.